This disclosure pertains to microlithography (pattern transfer) performed using a charged particle beam (e.g., electron beam or ion beam). Microlithography is a key technique used in the manufacture of microelectronic devices such as integrated circuits, displays, thin-film magnetic heads, and micromachines. More specifically, this disclosure pertains to stage apparatus that provide highly accurate and precise movement and positioning of, e.g., a reticle or substrate as used in a charged-particle-beam (CPB) microlithography apparatus. The stage apparatus also provide multiple degrees of freedom of stage movement with substantially reduced disturbance of the charged particle beam caused by magnetic fields generated by the stage apparatus.
In many types of industrial processes, it is important that the workpiece be held and moved in an accurate and precise manner. This need is especially acute in microlithography, in which pattern transfer must be performed under extremely high demands of positioning accuracy and precision.
In microlithography, the pattern-defining reticle and a substrate usually are mounted on respective stages that achieve positioning of the substrate and reticle relative to each other sufficient to permit the pattern defined on the reticle to be transferred to the substrate. To ensure maximal flexibility in positioning measurement and control, many degrees of freedom of movement of the stage are desirable. In photolithography, for example, stages have been devised that include a table provided with three degrees of freedom of movement (xcex8X, xcex8Y, and Z directions), wherein the table is mounted on a stage that is movable in the X, Y, and xcex8Z directions.
Photolithography systems do not include optical systems that dynamically correct the projected beam position. Hence, in photolithography systems, stage apparatus must be extremely accurate in their positioning ability and in their ability to synchronize motion with a second stage. To achieve such ends, a conventional stage apparatus for a photolithography system has a stacked two-level configuration as summarized above. Movements of the stage are performed by VCM (Lorentz-type xe2x80x9cvoice-coil motorxe2x80x9d) or EI core (electromagnetic) devices that utilize inexpensive electromagnetic power. These types of stage apparatus consume relatively low electrical power and have long service lives. Also, due to their simple configuration in which drive elements extend in respective linear directions, these types of stage apparatus are widely used in photolithography because they are relatively easy to control.
Stage apparatus conventionally used in photolithography, however, are not suitable for use in charged-particle-beam (CPB) microlithography systems. I.e, whenever a stage apparatus configured for use in photolithography is used in a CPB microlithography system, the following problems arise: (1) Since VCMs or electromagnets are used as drive means, as the stage is moved corresponding magnetic-field fluctuations are generated. These fluctuations cause minute deflections of the charged particle beam, which can have an adverse effect on the accuracy and precision of pattern transfer as achieved with the CPB microlithography system. (2) Use of magnetic and/or electrically conductive components in the stage and its drive mechanisms causes magnetic-field fluctuations as the stage is moved, which can have an adverse effect on the charged particle beam.
A conventional stage apparatus employs a biaxial air bearing for moving the stage in the X and Y directions. Such a stage apparatus is disclosed in Japan Kxc3x4kai Patent Publication No. Sho 62-182692, in which the stage apparatus includes multiple box-shaped air bearings. An oblique view of such a stage apparatus 140 is shown in FIG. 8. The stage apparatus 140 includes a base 141 to which two box-shaped base guides 142 are mounted. Each base guide 142 includes respective permanent-magnet plates mounted to the inner surfaces of the base guide 142, thereby forming a respective motor yoke 142a. Respective box-shaped coil bobbins 143 engage the respective xe2x80x9cupperxe2x80x9d (in the figure) portions of the base guides 142. Each combination of a motor yoke 142a and a coil bobbin 143 constitutes a respective linear motor that can be moved in the X-direction.
A box-shaped movable guide 144 extends between the two coil bobbins 143. A permanent magnet plate (not detailed) is mounted to the inner surface of the movable guide 144 to form a motor yoke 144a. A box-shaped coil bobbin 145 is engaged with the xe2x80x9cupperxe2x80x9d portion of the movable guide 144. The motor yoke 144aand coil bobbin 145 collectively constitute a linear motor providing movement in the Y-direction. A stage 146 is mounted to the coil bobbin 145. A substrate or reticle can be mounted to the stage 146.
Each coil bobbin 143, 145 includes air jets (not shown) defined in the respective inner surfaces thereof, facing the respective motor yokes 142a, 144a, thereby forming respective air bearings.
Whenever a stage apparatus as shown in FIG. 8 is used in a CPB microlithography system, the following problems may arise: (1) Since VCMs or electromagnets are used for actuating movement of the stage, moving the stage generates corresponding fluctuations in the magnetic field in the vicinity of the charged particle beam. These fluctuations adversely affect the charged particle beam, which decreases pattern-transfer accuracy and precision. (2) The stage apparatus 140 is configured such that X-Y movements involve respective movements along respective guides (coil bobbins 143 on base guides 142 for X-direction motion, and coil bobbin 145 on movable guide 144 for Y-direction motion) that are stacked relative to each other. Hence, to provide movement along the lower of these axes (in this instance the X-axis) a large and heavy movement mechanism must be employed.
Another conventional stage apparatus that provides motion in the X- and Y-directions comprises two uni-axial drives each configured in a respective xe2x80x9cHxe2x80x9d configuration. More specifically, the two uni-axial drives are arranged at 90xc2x0 relative to each other. Such a configuration eliminates the need for respective permanent magnets on the xe2x80x9cinnerxe2x80x9d surfaces of the movable guide 144. Also, in this configuration, the stage is freely movable in the Y-direction on the movable guide 144 instead of on the coil bobbin 145. But, two stages 145xe2x80x2 must be provided, wherein one stage is rigidly mounted on top of the other. By placing the drive actuators at respective ends of the movable guide, the effects of magnetic fluctuations on the charged particle beam are minimized, with a corresponding improvement of pattern-transfer accuracy and precision. However, because the two stages are rigidly fixed to each other, their relative movements are too restricted. I.e., the operation of one stage is affected whenever the other stage is being actuated, which decreases the positioning-control accuracy of the stage apparatus. In addition, whenever two stages are rigidly fixed to each other in this manner, extremely high accuracy and precision must be applied during assembly of the stage apparatus.
In view of the shortcomings of the prior art as summarized above, an object of the invention is to provide stage apparatus, for use in charged-particle-beam (CPB) microlithography apparatus, in which the stage table can be driven in multiple degrees of freedom with minimal magnetic disturbance to the charged particle beam, thereby improving the accuracy with which stage position can be controlled.
To such end, and according to a first aspect of the invention, stage apparatus are provided. An exemplary embodiment of a stage apparatus includes an XY stage that is movable and positionable within an XY plane defined by mutually perpendicular X- and Y-axes that are perpendicular to a Z-axis. The stage apparatus also includes a first table that is mounted to the XY stage and that is configured to be driven in a xcex8Z drive direction about the Z-axis. The apparatus also includes a second table that is mounted to the first table and that is configured to be driven in a xcex8X drive direction about the X-axis, a xcex8Y drive direction about the Y-axis, and in a Z-axis drive direction. Thus, a stage apparatus is realized that provides multiple degrees of freedom of motion of the stage. Also, by disposing the various drive axes in separate tables, control of the stage and of the tables is made simpler without sacrificing accuracy and precision.
In this embodiment the XY stage can comprise respective X-axis and Y-axis linear motors configured to impart motion of the XY stage in the XY plane. The first and second tables can be connected together using multiple flexures, wherein the flexures are configured to prevent movement of the first and second tables relative to each other outside the drive directions.
The first and second tables and the XY stage desirably are connected together, at least in part, by actuators that are configured to drive the first and second plates and the XY stage in the respective drive directions. Also, the XY stage and actuators desirably are non-magnetic and non-conductive, especially if the stage apparatus is to be used in a charged-particle-beam system.
A stage apparatus according to another embodiment includes an XY stage that is movable and positionable within an XY plane. The apparatus also includes a first table that is mounted to the XY stage and that is configured to be driven in a xcex8X drive direction about the X-axis, a xcex8Y drive direction about the Y-axis, and in a Z-axis drive direction. The apparatus also includes a second table that is mounted to the first table and that is configured to be driven in a xcex8Z drive direction about the Z-axis.
As in the first embodiment, the XY stage can include respective X-axis and Y-axis linear motors configured to impart motion of the XY stage in the XY plane. The stage apparatus also can include multiple flexures connecting the first and second plates together. Also, the first and second plates and the XY stage can be connected together, at least in part, by actuators that are configured to drive the first and second plates and the XY stage in the respective drive directions.
A stage apparatus according to yet another embodiment includes multiple stationary Y-axis guides that are parallel to each other and that extend in a Y-axis direction. A respective Y-axis slider is engaged with each stationary Y-axis guide. Each Y-axis slider is configured to slide in the Y-axis direction relative to the respective stationary Y-axis guide. A movable X-axis guide extends in an X-axis direction between the Y-axis sliders and connects the Y-axis sliders together. The apparatus includes an X-axis stage that is mounted to the movable X-axis guide and that is configured to slide in the X-axis direction along the movable X-axis guide. The apparatus includes multiple stationary X-axis guides that are parallel to each other and that extend in a X-axis direction. A respective X-axis slider is engaged with each stationary X-axis guide. Each X-axis slider is configured to slide in the X-axis direction relative to the respective stationary X-axis guide. A movable Y-axis guide extends in a Y-axis direction between the X-axis sliders and connects the X-axis sliders together. The stage apparatus also includes a Y-axis stage that is mounted to the movable Y-axis guide and that is configured to slide in the Y-axis direction along the movable Y-axis guide, wherein the X-axis stage and the Y-axis stage are connected together by multiple flexures that are rotatable within a plane perpendicular to the Z-axis. In this embodiment, since the X-axis stage and Y-axis stage are connected together by flexures, each of these stages can move smoothly without being restricted by the other stage, thereby improving the accuracy and precision of stage-positioning control.
According to another aspect of the invention, microlithography apparatus are provided that include a stage apparatus such as any of the embodiments summarized above.
The foregoing and additional features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.